JP2015074130A - Droplet discharge device and droplet discharge method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a reduction in image quality due to maintenance processing which is executed while printing is being performed.SOLUTION: A droplet discharge device comprises: a discharge section for discharging droplets; and a controller which executes main scanning direction recording operation for recording dots by discharging the droplets in a main scanning direction of a medium and sub-scanning operation for relatively moving the medium and the discharge section in a sub-scanning direction intersecting with the main scanning direction and controls printing operation for recording the dots onto the medium by performing multi-pass recording to be completed by performing recording of the dots positioned on one main scanning line in the main scanning direction N times (n is an integer of 2 or more) and maintenance operation for performing maintenance with respect to the discharge section. When executing the maintenance operation multiple times, the controller controls the maintenance operation so as to execute the main scanning direction recording operation at least (N-1) times during a period of time from when executing previous maintenance operation to when executing following maintenance operation.

Description

  The present invention relates to a droplet discharge device.

  In a serial-type inkjet printer, a main scanning path for forming dots by ejecting ink from nozzles of the print head while moving the print head and the medium relatively in the main scanning direction, and a sub-scanning crossing the main scanning direction. By repeating sub-scanning in which the medium is relatively moved in the scanning direction, dots are formed on a plurality of raster lines arranged in the sub-scanning direction, and an image is printed on the medium. In addition, as a method of forming dots on a raster line, a single pass method in which formation of dots on a raster line is completed in one main scanning pass and a main scanning pass of N times (N is an integer of 2 or more). And a multi-pass method for completing the formation of dots on the raster line.

  In an ink jet printer, there are cases where the nozzles are clogged due to an increase in the viscosity of the ink or air bubbles are mixed, so that the ink cannot be ejected. When the nozzles are clogged, dots are lost in the image, which causes the image quality to deteriorate. Therefore, in order to suppress deterioration in image quality due to defective ink ejection from the nozzles, a conventional ink jet printer may perform nozzle check and head cleaning (wiping, ink suction, flushing, etc.). For example, in Patent Document 1, during continuous printing in which printing is continuously performed on a plurality of labels, if the number of continuous printing count passes (corresponding to the number of main scanning passes) exceeds a threshold, printing is in progress. However, there is disclosed a technique for avoiding a printing defect caused by occurrence of a nozzle (hereinafter, also referred to as “defective nozzle”) in which nozzle inspection is performed and ink ejection is defective. At this time, as a threshold value for the number of count passes, a small value is used in a printing mode with a high setting reliability, and conversely, a large value is used in a printing mode with a low setting reliability. Accordingly, the timing of nozzle inspection changes according to the print setting reliability. In the following, processing for confirming the ejection state of the head and processing for restoring the ejection state of the head, such as nozzle inspection and head cleaning, are also referred to as “maintenance processing”.

JP 2010-30184 A

  Here, in the ink jet printer, in order to suppress the deterioration of the image quality of the image due to the printing failure caused by the occurrence of the defective nozzle described above, it is desirable to perform as many maintenance processes as possible even during the printing. ing. However, the execution of the maintenance process during printing has the following problems.

  When maintenance processing is executed during printing on one medium, the dots formed in the main scanning pass immediately before the maintenance processing and the main scanning pass immediately after the maintenance processing are formed depending on the time stopped by the maintenance processing. There is a problem in that a difference occurs in the formation state with respect to the formed dots, and a deterioration in image quality due to color unevenness due to the difference may occur. For example, in the multi-pass method, the dots in the main scanning pass immediately before the maintenance processing and the dots in the main scanning pass immediately after the maintenance processing are mixed in a plurality of dots arranged in one raster line. Color irregularities may appear.

  Note that the above-described problem is not limited to serial inkjet printers, and is a problem common to droplet discharge apparatuses that record dots by discharging droplets onto a medium.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms.

(1) According to the embodiment of the present invention, a droplet discharge device for recording dots on a medium is provided. The droplet discharge apparatus includes: a discharge unit that discharges droplets; a main scanning direction recording operation that records dots by discharging the droplets along the main scanning direction of the medium; and the main scanning direction. A sub-scanning operation is performed in which the medium and the ejection unit are relatively moved in the crossing sub-scanning direction, and dots recorded on one main scanning line along the main scanning direction are recorded N times (N is And a control unit that controls a printing operation for recording dots on the medium and a maintenance operation for performing maintenance on the ejection unit by performing multipass recording that is completed in the main scanning direction recording operation of 2 or an integer). And comprising; The controller, when performing a plurality of maintenance operations, performs at least (N-1) main scanning direction recording operations from the execution of the previous maintenance operation to the execution of the next maintenance operation. Control to execute. According to the droplet discharge device of this aspect, during the printing operation executed by multi-pass printing that is completed in N main scanning passes, the maintenance process is performed at the maintenance interval of (N-1) or more main scanning passes. It can be performed in a distributed manner. As a result, it is possible to suppress the appearance of color unevenness caused by performing the maintenance process during the printing operation, and to suppress the deterioration of the image quality of the printed image.

(2) In the liquid droplet ejection apparatus of the above aspect, the main scanning direction recording operation is an operation of ejecting the liquid droplets from the ejection unit while relatively moving the ejection unit and the medium in the main scanning direction. Also good. In this case, it is possible to perform maintenance on the ejection unit that moves relative to the medium.

(3) In the droplet discharge device of the above aspect, a time during which the printing operation is interrupted by one maintenance operation is limited to an allowable time or less, and a maintenance process in which the time required for completion is equal to or more than the allowable time is You may make it divide | segment into the several maintenance operation | movement below permissible time. By executing the maintenance process for the allowable time or longer during the printing operation, it is possible to suppress the appearance of color unevenness and suppress the deterioration of the image quality of the printed image.

(4) In the liquid droplet ejection apparatus according to the above aspect, the control unit performs the first mode in which the multipass recording parameter N is N ₁ and N ₂ (N ₂ is an integer greater than N ₁ ). The printing operation can be controlled in any one of the second mode; in the first mode, at least from the execution of the previous maintenance operation to the execution of the next maintenance operation. Control is performed so as to execute the (N ₁ -1) first number of main scanning direction recording operations; in the second mode, the next maintenance operation is executed after the previous maintenance operation is executed. In the meantime, it may be controlled to execute at least (N ₂ −1) times of the main scanning direction recording operation. According to the droplet discharge device of this aspect, the maintenance operation can be distributed and executed at intervals suitable for each mode.

(5) In the droplet discharge device of the above aspect, the first number of times and the second number of times may be set to an equal value. In this way, maintenance operations can be distributed and executed at regular intervals regardless of the mode, and the processing can be simplified.

(6) In the droplet discharge device of the above aspect, the maintenance process includes (i) a nozzle inspection for inspecting a nozzle state of the discharge unit, (ii) a flushing for empty discharge of the droplet from the discharge unit, iii) It may be configured to include at least one of wiping and wiping off the surface of the discharge unit on which the nozzle is provided. In this case, during the printing operation, the occurrence of color unevenness caused by executing at least one maintenance process of nozzle inspection, flushing, and wiping is suppressed, and the deterioration of the image quality of the recorded image is suppressed. be able to.

(7) In the droplet discharge device of the above aspect, the droplet may be ink containing resin. In this case, the droplet discharge device using the ink containing the resin uses a structure in which the resin is cured and a resin film is formed on the medium so that the ink is fixed to the medium. The ink hardens in the nozzles and tends to clog. Therefore, in a droplet discharge device that uses resin-containing ink, maintenance processing is performed during the printing operation, thereby effectively suppressing clogging of the nozzles of the discharge unit and suppressing deterioration in image quality. it can.

Note that the present invention can be realized in various modes as described below.
(A) A droplet discharge device and a droplet discharge control device.
(B) A droplet discharge method and a droplet discharge control method.
(C) A computer program for realizing the above apparatus and method.
(D) A non-transitory storage medium on which a computer program for realizing the above apparatus and method is recorded.

1 is a schematic perspective view showing a main configuration of a color inkjet printer as an embodiment of a droplet discharge device of the present invention. FIG. 2 is a block diagram illustrating an electrical configuration of a printer. It is explanatory drawing which shows an example of a structure of the nozzle provided in the print head. It is explanatory drawing shown about the printing by multipass recording. It is a schematic diagram for demonstrating the test | inspection of each nozzle by a nozzle test | inspection part. It is a schematic diagram for demonstrating the flushing process of each nozzle of a print head. It is a schematic diagram for demonstrating the wiping process of the nozzle surface of the print head by a wiper part. It is explanatory drawing which shows the management procedure of the maintenance operation | movement at the time of performing a maintenance operation | movement during printing operation. It is explanatory drawing shown about the case where a some maintenance process is distributed as an Example. It is explanatory drawing shown about the case where a some maintenance process is not disperse | distributed as a comparative example.

A. Embodiment:
A1. Configuration of printing device:
FIG. 1 is a schematic perspective view showing a main configuration of a color inkjet printer 20 as an embodiment of a droplet discharge device of the present invention. The printer 20 includes a paper feed roller 24 driven by a paper feed motor (not shown), a platen plate 26, a carriage 28, a carriage motor 30, a traction belt 32 driven by the carriage motor 30, and a carriage 28. The guide rail 34 is provided. On the carriage 28, a print head 40 having a large number of nozzles and a plurality of ink cartridges 41 are mounted. The print head 40 functions as an ejection unit that ejects droplets. Specifically, as the plurality of ink cartridges 41, a black ink cartridge 41k, a cyan ink cartridge 41c, a magenta ink cartridge 41m, and a yellow ink cartridge 41y are mounted.

  In the maintenance position MP of the carriage 28 at the right end of FIG. 1, a nozzle inspection unit 100 and an ink receiving container 210 are provided. The nozzle inspection unit 100 includes a light emitting element 102a and a light receiving element 102b, and inspects for missing dots by examining the flight state of ink droplets ejected from the nozzles using these elements 102a and 102b. Detailed contents of the inspection by the nozzle inspection unit (hereinafter also referred to as “nozzle inspection” or “dot missing inspection”) will be described later. The ink receiving container 210 also serves as an ink receiving container for ink that is ejected from the nozzles during nozzle inspection and flushing described later.

  A wiper unit 300 is provided at a position between the ink receiving container 210 and the platen plate 26. The wiper unit 300 includes a wiper blade 312 held by a wiper holding unit 314, and performs so-called wiping to wipe off dirt around the nozzles of the print head 40. The detailed contents of wiping by the wiper unit will be described later.

  The carriage 28 is pulled by the pulling belt 32 and moves along the guide rail 34 in the main scanning direction. As the carriage 28 moves in the main scanning direction, the ink cartridge 41 and the print head 40 also move in the main scanning direction. The printing paper (medium) P is taken up by a paper feed roller 24 from a paper stacker (not shown) and fed on the surface of the platen plate 26 in the sub-scanning direction. The main scanning direction is perpendicular to the sub-scanning direction. However, the sub-scanning direction and the main scanning direction do not necessarily need to be orthogonal to each other, and need only intersect. Although printing paper is used as the medium, a medium made of material other than paper may be used. Specifically, a material medium such as cloth or vinyl chloride resin may be used.

  After the movement of the printing paper P in the sub-scanning direction (paper feeding), ink droplets are ejected from nozzles (described later) arranged in the printing head 40 when the printing head 40 moves in the main scanning direction. Thus, formation of dots on the main scanning line along the main scanning direction of the printing paper P is executed. Thus, the movement of the print head 40 in the main scanning direction and the ejection of ink droplets onto the main scanning line are called main scanning, and one main scanning is called “main scanning pass” or simply “pass”. " The movement of the printing paper P in the sub scanning direction is called sub scanning.

  By repeating the sub-scanning operation and the main scanning operation alternately, a plurality of raster lines composed of a plurality of dots arranged on the main scanning line along the main scanning direction are formed side by side along the sub-scanning direction, Printing of an image on the printing paper P is executed.

  FIG. 2 is a block diagram illustrating an electrical configuration of the printer 20. The printer 20 includes an interface 50 that receives a signal supplied from the host computer 10 and a system controller 52 that controls the operation of the entire printer 20. The system controller 52 can operate as a print control unit 52a and a maintenance control unit 52b. The system controller 52 functions as a control unit that controls various operations of the printer 20.

  The system controller 52 is configured by a computer such as a microcomputer including a CPU (not shown) and a memory such as a ROM or a RAM. The system controller 52 functions as, for example, a print control unit 52a and a maintenance control unit 52b, and performs operations of the main scanning drive unit 54, the sub-scanning drive unit 56, the head drive unit 60, the nozzle inspection drive unit 62, and the wiper drive unit 64. Control.

  The main scanning drive unit 54 drives a main scanning drive mechanism including the carriage motor 30, the pulling belt 32, and the guide rail 34. In the printing operation, the main scanning drive unit 54 performs the movement of the carriage 28, that is, the print head 40 in the main scanning described above according to the control of the system controller 52 (printing control unit 52a). In the maintenance operation, the main scanning drive unit 54 executes the movement of the print head 40 to the maintenance position MP according to the control of the system controller 52 (maintenance control unit 52b).

  The sub-scanning drive unit 56 drives a sub-scanning driving mechanism including a paper feed motor (not shown) and the paper feed roller 24. The sub-scan driving unit 56 performs the movement (paper feed) of the printing paper P in the sub-scan described above according to the control of the system controller 52 (print control unit 52a). However, the sub-scanning operation may move the print head 40 instead of the printing paper P.

  In the printing operation, the head drive unit 60 drives the nozzles provided in the print head 40 according to the print data transferred from the host computer 10 according to the control of the system controller 52 (print control unit 52a). Ink droplets are ejected during scanning to form dots according to print data. In the maintenance operation, the head drive unit 60 performs idle ejection of ink from the nozzles at the above-described maintenance position MP in accordance with the control of the system controller 52 (maintenance control unit 52b). The so-called flushing, which is ejected from the nozzle, is performed. Therefore, the head driving unit 60 also operates as a flushing unit. Note that “empty ejection” means ejection performed for purposes other than the original use (ie, printing) of ink droplets.

  The nozzle inspection driving unit 62 performs nozzle inspection described later according to the control of the system controller 52 (maintenance control unit 52b). Further, the wiper driving unit 64 performs wiping described later under the control of the system controller 52 (maintenance control unit 52b).

  FIG. 3 is an explanatory diagram illustrating an example of the configuration of the nozzles provided in the print head 40. On the lower surface (hereinafter also referred to as “nozzle surface”) 45p of the print head 40, a black ink nozzle row NLk, a cyan ink nozzle row NLc, a magenta ink nozzle row NLm, and a yellow ink nozzle row NKy are provided. . In the following description, when colors are not particularly distinguished, they are simply referred to as “nozzle rows NL”. Each nozzle row NL includes a plurality of nozzles NZ arranged in the sub-scanning direction SS at a constant nozzle pitch. Note that the sub-scanning direction SS indicates the relative movement direction of the printing paper P and the print head 40. In the present embodiment, the nozzle pitch dp and the pixel pitch in the sub-scanning direction on the printing paper P are equal. However, the nozzle pitch dp can be an integer multiple of twice or more the pixel pitch in the sub-scanning direction on the printing paper P. In the latter case, so-called interlaced recording (a recording method in which dots are formed in the second and subsequent passes on the other main scanning lines existing between the main scanning lines in which dots are formed in the first pass) is executed. Is done.

A2. Printing operation overview:
The printing operation is an operation for recording dots on a medium. FIG. 4 is an explanatory diagram showing printing by multipass printing. Here, the position of the nozzle row NL in three main scanning passes and the printing area at that position are shown. Further, for convenience of illustration, the printing head 40 is shown moving in the sub-scanning direction SS with respect to the printing paper P.

  Here, “multi-pass printing” means a dot printing method in which the formation of dots on individual main scanning lines (raster lines) is completed in N times (N is an integer of 2 or more) main scanning passes. This is also called “multi-pass printing”. The example of FIG. 4 shows a case where the number N of passes in multi-pass printing (hereinafter also referred to as “multi-pass number N”) is 3. In the first pass (1PS), the second pass (2PS), and the third pass (3PS), the position of the nozzle row NL is a distance corresponding to 1/3 of the head height Hh. Deviation in the sub-scanning direction. Here, “head height Hh” means a distance represented by m × dp (m is the number of nozzles in the nozzle row 95 and dp is the nozzle pitch). In the example of FIG. 4, the number of nozzles m is 9, and a state in which three nozzles are shifted in the sub-scanning direction for each main scanning pass is shown.

  Here, a case where dots are formed on all pixels of the printing paper P using one color ink (for example, cyan ink) will be described as an example. In the first pass, dot formation is performed in the regions Q1 to Q3. In the second pass, dots are formed in the regions Q2 to Q4. In the third pass, dot formation is executed in the regions Q3 to Q5. Since three main scanning passes are executed on each main scanning line, dot recording is not executed at all pixel positions on each main scanning line, but only a part thereof is executed in each main scanning pass. . Further, when three main scanning passes are completed on each main scanning line, dot recording is completed at all pixel positions on the main scanning line. In this specification, the term “dot recording” means “performing dot formation or non-formation”.

A3. Maintenance operation overview:
The maintenance operation is an operation for executing a maintenance process. The maintenance process for the print head 40 includes at least one of the three types of maintenance processes of nozzle inspection, flushing, and wiping. These maintenance processes are performed at various timings such as when the printing apparatus is started or shut down, when printing is not executed, periodically, or when the user issues a maintenance instruction via a button (not shown). This is executed when a maintenance request occurs. During printing, maintenance requests are generated at various timings, and corresponding maintenance processing is executed as described later. Here, the contents of each maintenance process will be described.

(1) Nozzle Inspection FIG. 5 is a schematic diagram for explaining the inspection of each nozzle NZ by the nozzle inspection unit 100. The light emitting element 102a and the light receiving element 102b are disposed on both sides of the print head 40. In a state where the print head 40 is positioned at such a position that the nozzle row NLy is located above the optical path of the laser light L, the head driving unit 60 (FIG. 2) sets each nozzle of the nozzle row NLY one by one The ink droplets are sequentially ejected from the respective nozzles by sequentially driving each of the driving periods. Since the ejected ink droplet interrupts the optical path of the laser beam L on the way, the light reception by the light receiving element 102b is temporarily interrupted. Therefore, if the ink droplets are normally ejected from a certain nozzle, the laser light L is temporarily blocked by the light receiving element 102b, so that it can be determined that the nozzle is not clogged. Further, when the laser light L is not shielded at all within the drive period of a certain nozzle, it can be determined that the nozzle is clogged. In addition, as a nozzle test | inspection, the test | inspection of methods other than such an optical test | inspection can also be utilized. For example, when the actuator of the nozzle is a piezo element, an inspection method for inspecting whether ink droplets can be normally ejected from individual nozzles by measuring the residual vibration after vibration is applied to the piezo element May be adopted.

(2) Flushing FIG. 6 is a schematic diagram for explaining the flushing process of each nozzle NZ of the print head 40. In the flushing process, the head driving unit 60 drives each nozzle NZ to execute idle ejection of ink droplets.

(3) Wiping FIG. 7 is a schematic diagram for explaining the wiping process (wiping process) of the nozzle surface 45 p of the print head 40 by the wiper unit 300. The nozzle surface is a surface on which nozzles are provided. The nozzle surface 45p may become dirty due to thickened ink adhering to the nozzle opening. In addition, ink stains may adhere to the nozzle surface 45p due to contact with the end surface of the ink receiving container 210. If dirt on the nozzle surface 45p accumulates, the performance of the print head 40 deteriorates. In the wiping process, by moving the print head 40 in the arrow X direction (main scanning direction (MS)), the dirt on the nozzle surface 45p can be wiped off by the tip 312e of the wiper blade 312.

A4. Maintenance operation during printing operation:
FIG. 8 is an explanatory diagram showing a maintenance process management procedure when the maintenance process is executed during a printing operation on one medium. The maintenance control unit 52b (see FIG. 2) starts the maintenance management shown in FIG. 8 in accordance with the start of the printing operation by the multipass recording described above until the printing operation on one medium is completed (step (S10: YES), Steps S20 to S90 are repeated.

  In step S20, during the printing operation, an execution request for at least one of the plurality of types of maintenance processes is generated, and the process waits while it is not determined that “maintenance is present”. If there is a request for maintenance processing, a pass number (pass number) Pn (Pn is an integer of 1 or more) of the main scanning pass currently being executed is acquired from the print control unit 52a (step S30). As the maintenance execution request, for example, according to the set management schedule, a maintenance processing execution request among nozzle inspection, flushing, and wiping is appropriately generated. Further, it is preferable that the time Tm for stopping printing for one maintenance operation (hereinafter referred to as “stop time Tm”) is set to be equal to or less than a predetermined time limit Tr. This time limit Tr is set in consideration of the influence on the occurrence of color unevenness due to the stop of printing. For this reason, the maintenance process that requires a longer time than the time limit Tr is executed by being divided into a plurality of maintenance operations. For example, it is assumed that the time required for inspection of a large number of nozzles provided in the print head is longer than the time limit Tr. Therefore, the nozzle inspection can be performed by dividing the operation into a plurality of operations for performing the inspection for a predetermined number of nozzles. Further, when the printing apparatus has a large number of print heads, the inspection operation may be executed for each predetermined number of print heads for flushing and wiping. In this specification, one operation performed within the time limit Tr is referred to as a “maintenance operation”. In addition, processing performed in response to one maintenance request is referred to as “maintenance processing”. Therefore, one maintenance process is completed by one or more maintenance operations.

  If the generated maintenance request is the first request during a printing operation on one medium in step S40, the process proceeds to step S60 described later. On the other hand, when the generated maintenance request is not the first request during the printing operation, it is determined whether or not (Pn−Pm) <Mi is satisfied (step S50). Here, Pm is the pass number of the main scanning pass executed immediately before the previous maintenance operation. Mi is a threshold for determining whether or not a sufficient number of paths have been executed between these path numbers Pn and Pm, and is a value equal to or greater than (N−1) (N is a multipath). Number). Hereinafter, (Pn−Pm) is referred to as “the number of elapsed paths”. When the number of elapsed paths (Pn−Pm) is less than the interval Mi, the process returns to step S30 and steps S30 to S50 are repeated. On the other hand, when the number of elapsed passes (Pn−Pm) becomes equal to the interval Mi, the process proceeds to step S60, and printing is performed after the main scanning pass of the currently executed pass number Pn is completed to the print control unit 52a. Instructs to pause the operation. The print control unit 52a instructed to stop the printing operation temporarily stops the printing operation when the main scanning pass currently being executed is finished.

  The threshold value Mi for the number of elapsed passes (Pn−Pm) is determined based on various maintenance execution times such as nozzle inspection execution time and flushing execution time. Further, the value of the threshold value Mi may be set based on a predetermined number of passes, a number of passes corresponding to a preset print area, or the like. Further, the value of the threshold value Mi only needs to be set so that at least one maintenance is performed during printing.

  The maintenance control unit 52b performs the requested maintenance operation after the printing operation is temporarily stopped (step S70). As described above, the stop time Tm for one maintenance operation is set to be equal to or shorter than the predetermined time limit Tr. After the maintenance operation is completed, the print control unit 52a is instructed to cancel the temporary stop of the print operation (step S80). The print control unit 52a instructed to cancel the temporary stop of the printing operation resumes the printing operation from the next main scanning pass. Then, the maintenance control unit 52b sets Pm = Pn (step S90), and repeatedly executes the processing of step S10 to step S90 until the printing operation on one medium is completed.

  In the flow of FIG. 8, the reason why the maintenance operation is executed when the number of elapsed paths (Pn−Pm) becomes equal to the threshold value Mi is to prevent the maintenance operation from being excessively concentrated in a short time. . That is, even when a maintenance request is generated, the maintenance operation is not executed until the number of elapsed paths (Pn−Pm) becomes equal to the threshold value Mi, so that the maintenance operation is not excessively concentrated in a short period of time. As described above, the threshold value Mi is preferably set to a value (N-1) or more (N is the number of multipaths) for the following reason. That is, in multi-pass printing, dot printing on each scanning line is completed in N main scanning passes. At this time, if the threshold value Mi is set to a value equal to or greater than (N−1), at least one maintenance operation is executed during the period from the start to the completion of dot recording on each main scanning line. Just do. Therefore, it is possible to suppress an excessively long time from the start to the end of dot recording on each scanning line, and as a result, it is possible to suppress color unevenness. Further, if the stop time Tm for one maintenance operation is limited to a predetermined time limit Tr or less, this effect can be further enhanced. Note that when the number N of multi-passes is 2, the threshold value Mi can be set to 1, so that the maintenance operation is allowed to be performed for each main scanning pass. However, also in this case, if the stop time Tm for one maintenance operation is set to be equal to or shorter than the predetermined limit time Tr, the recording timing of a certain dot and other timings on each scanning line It can be suppressed that an excessively long time elapses from the dot recording timing. However, the threshold value Mi is preferably set to a value of 2 or more regardless of the value of the multipath number N. By so doing, it is possible to secure a wider time interval for the maintenance operation, so that the effect of suppressing color unevenness can be further enhanced. The threshold value Mi is preferably set to a value smaller than the number of main scanning passes executed in the printing operation on one medium. In this way, it is possible to perform at least one maintenance operation during a printing operation on one medium.

  According to the maintenance processing management procedure described above, the interval of Mi (≧ N−1) main scanning passes is always opened from one maintenance operation to the next maintenance operation. For this reason, for example, even if a maintenance request that is divided and executed multiple times occurs, as in the nozzle inspection described above, after performing one maintenance operation, it is always necessary to perform the next maintenance operation. The interval of Mi main scanning passes is opened, and a plurality of maintenance operations are executed in a distributed manner.

  FIG. 9 is an explanatory diagram illustrating a case where a plurality of maintenance operations are distributed as an example. FIG. 10 is an explanatory diagram showing a case where a plurality of maintenance operations are not distributed as a comparative example. The embodiment of FIG. 9 is a multi-pass printing with a multi-pass number N of 3 and a maintenance process with a division number Q of 4 during the execution of the main scanning pass with Pn = 1 (maintenance process executed in four divided steps). ) Is requested, and the interval Mi is set to 2 (= N−1). In the comparative example of FIG. 10, similarly to the embodiment, multipass printing with a multipass number N of 3 requires maintenance processing with a division number Q of 4 during execution of the main scanning pass with Pn = 1, and the interval Mi. In other words, there is no setting, that is, the interval Mi is 0, and four maintenance operations are executed once every time between the main scanning pass and the main scanning pass. The stop time Tm in each maintenance operation will be described as the same time for easy explanation.

  In the comparative example (FIG. 10), Q (= 4) maintenance operations are sequentially executed after the end of each main scanning pass of Pn = 1 to 4. In this case, in the raster lines with raster numbers 7 to 15, (N−1) · Tm (= 2 · Tm) stop times are accumulated during N (= 3) main scanning passes. For this reason, in these raster lines, as described in the problem, there is a difference in the formation state between the dots formed in each of the N main scanning passes, and thereby, along the main scanning direction. Color unevenness is easily noticeable. In addition, a number of raster lines in which (N-1) stop times are accumulated are continuous along the sub-scanning direction, and color unevenness along the sub-scanning direction is easily noticeable. Therefore, in the case of this comparative example, the occurrence of color unevenness is concentrated and becomes conspicuous, and there is a possibility that deterioration in image quality becomes obvious.

  On the other hand, in the embodiment (FIG. 9), after each main scanning pass of Pn = 1, 3, 5, and 7, the maintenance operation is executed in a distributed manner at intervals Mi (= N−1 = 2). The In this case, on the raster lines of raster numbers 7 to 26, only one stop time Tm occurs during N (= 3) main scan passes, and the stop time is accumulated. Absent. For this reason, in these raster lines, there is a considerable difference in the formation state between the dot formation state in the main scanning pass immediately before the maintenance process is executed and the dot in the main scanning pass immediately after the maintenance processing, but the maintenance operation Since the difference in dot formation state is reduced between main scanning passes that are continuously executed without being performed, the occurrence of color unevenness is dispersed. As a result, it is possible to suppress deterioration in image quality by suppressing the appearance of uneven color compared to the comparative example. In the above embodiment, the printing operation on one medium has been described as an example. However, the present invention may be applied to a printing operation in one print job. For example, when the medium is a roll, the present invention is applied to a printing operation in one print job.

B. Variation:
(1) In the above embodiment, the limit time Tr of the print stop time Tm for the maintenance operation has been described as the time set in consideration of the influence on the print time. On the other hand, the time limit Tr may be set to the time set as follows.

  As described in the problem, the dots formed in the main scanning pass immediately before the maintenance operation and the dots formed in the main scanning pass immediately after the maintenance operation are based on the time (stop time Tm) interrupted by the maintenance operation. There is a problem in that there is a difference in the formation state between the two, and color unevenness due to the difference is manifested to deteriorate the image quality. Therefore, the time limit Tr may be set based on the permissible time so that the degradation of the image quality is allowed even if it is interrupted. In this way, the difference in the formation state between the dots formed in the main scanning pass immediately before the maintenance operation and the dots formed in the main scanning pass immediately after the maintenance operation is suppressed, resulting from this. This makes it possible to suppress the appearance of uneven color and to suppress the deterioration of image quality. Note that the allowable time is obtained by confirming in advance a time that falls within a range in which the deterioration in image quality is allowed even if the printing operation is interrupted. The allowable time may be set based on a user input.

(2) The above embodiment has been described as a printing apparatus that performs printing with N multi-passes. On the other hand, in a printing apparatus that performs multipass printing, the first mode in which the number of multipasses is N _{1 and} the second mode in which the number of multipasses is N ₂ (N ₂ is an integer greater than N ₁ ). In addition, there is a printing apparatus that can perform printing by switching to either the first mode or the second mode. In the case of such a printing apparatus, the following may be performed.

The interval of the maintenance operation in the first mode with the number of multi-passes N ₁ is set to the interval Mi _{1 of the} number of main scanning passes of (N ₁ −1) or more, and the maintenance operation in the second mode with the number of multi-passes N ₂ The interval Mi ₂ may be set to (N ₂ −1) or more, and the intervals Mi ₁ and Mi ₂ in the two modes may be set to different values. In this case, the maintenance operation can be distributed and executed at appropriate intervals in each of the first mode and the second mode.

Further, the maintenance operation interval Mi ₁ in the first mode may be set to the same interval as the maintenance operation interval Mi ₂ in the second mode. In this way, maintenance operations can be executed in a distributed manner at regular intervals during printing regardless of the mode, and the processing can be simplified.

  Also, in a printing apparatus that has three or more different multi-pass modes instead of two modes, set appropriate maintenance operation intervals in each mode, and perform maintenance operations in a distributed manner. Alternatively, the maintenance operation in each mode may be distributed and executed at intervals of the mode having the largest number of multipaths regardless of the mode.

(3) In the above embodiment, a printing apparatus has been described that can perform nozzle inspection, flushing, and wiping as maintenance processes during printing. On the other hand, maintenance such as a printing apparatus capable of performing both flushing and wiping, a printing apparatus capable of performing both nozzle inspection and flushing, and a printing apparatus capable of performing only flushing, include nozzle inspection, flushing, and The present invention is applicable to a printing apparatus capable of executing at least one of wiping.

(4) In the above-described embodiment, the serial type printing apparatus in which the print head moves in the main scanning direction has been described. However, in the present invention, the entire width of the medium along the main scanning direction with the print head stopped is described. The present invention can also be applied to a printing apparatus that can execute dot recording over (that is, the entire length of the main scanning line). In this case, the movement of the print head (or medium) in the main scanning direction (main scanning) is not performed, but the movement of the medium (or print head) in the sub scanning direction (sub scanning) is preferably executed. Also in this case, the multi-pass printing can be executed in substantially the same manner as in the above embodiment.

  There are devices that do not move the print head and the medium in the main scanning direction, and devices that do it. In both cases, the dot recording that is performed on the main scanning line is the “main scanning direction recording operation”. Can be called. That is, in an apparatus that does not perform main scanning of the print head, the “main scanning direction recording operation” is an operation of executing dot recording on each main scanning line while the print head is stopped with respect to the medium. On the other hand, in the apparatus that performs the main scanning of the print head, the “main scanning direction recording operation” is an operation of executing dot recording on each main scanning line while the print head and the medium move relatively in the main scanning direction. This corresponds to the main scanning pass. In other words, the main scanning direction recording operation is a main scanning direction recording operation for recording dots by discharging droplets along the main scanning direction of the medium. In addition, the above-described multi-pass printing, in other words, completes printing of dots positioned on one main scanning line along the main scanning direction by N times (N is an integer of 2 or more). It is.

(5) In the said embodiment, it does not specifically limit about the ink used, It is applicable to the printing apparatus which uses various ink. For example, it is effective in a printing apparatus that uses an ink containing a resin (resin-based ink). For example, a resin-based ink such as a resin ink containing an aqueous binder (special polymer) that cures at a low temperature is cured at a low temperature (usually about 40 ° C. to 60 ° C.) to form a resin film on the medium. Thus, a structure in which the ink is fixed to the medium is used, and the ink is hardened and clogged easily in the nozzles of the print head. For this reason, in a printing apparatus that uses resin-based ink, performing maintenance processing even during printing is an effective means for suppressing clogging of the nozzles of the print head and suppressing deterioration in image quality. . In addition, there is no limitation in particular in resin-type ink, It can apply to the printing apparatus which uses various resin-type ink.

(6) The above embodiment has been described as a printing apparatus that performs multi-pass printing in which dot formation on a raster line (main scanning line) is completed N times (N is an integer of 2 or more). In addition to this multi-pass printing, a printing apparatus that performs interlaced recording, which is a printing method in which a raster line in which dots are not formed is sandwiched between raster lines in which dot formation is completed in N main scanning passes It is also applicable to.

(7) In the above-described embodiments, the printing apparatus that ejects ink onto the printing paper has been described. However, the present invention is applicable to various apparatuses that record dots by ejecting droplets onto a medium. Such an apparatus is called a liquid ejecting apparatus, a droplet discharge apparatus, or the like. In addition, a droplet means the state of the liquid discharged from the said liquid ejecting apparatus, and shall also include what pulls a tail in granular shape, tear shape, and thread shape. The liquid here may be any material that can be ejected by the liquid ejecting apparatus. For example, it may be in the state when the substance is in a liquid phase, such as a liquid state with high or low viscosity, sol, gel water, other inorganic solvents, organic solvents, solutions, liquid resins, liquid metals (metal melts ) And a liquid as one state of a substance, as well as a material in which particles of a functional material made of a solid such as a pigment or metal particles are dissolved, dispersed or mixed in a solvent. Further, representative examples of the liquid include ink and liquid crystal as described in the above embodiment. Here, the ink includes general water-based inks and oil-based inks, and various liquid compositions such as gel inks and hot melt inks. As a specific example of the liquid ejecting apparatus, for example, a liquid containing a material such as an electrode material or a color material used for manufacturing a liquid crystal display, an EL (electroluminescence) display, a surface emitting display, a color filter, or the like in a dispersed or dissolved state. It may be a liquid ejecting apparatus for ejecting. Further, it may be a liquid ejecting apparatus that ejects a bio-organic matter used for biochip manufacture, a liquid ejecting apparatus that ejects a liquid as a sample that is used as a precision pipette, a printing apparatus, a microdispenser, or the like. In addition, transparent resin liquids such as UV curable resin to form liquid injection devices that pinpoint lubricant oil onto precision machines such as watches and cameras, and micro hemispherical lenses (optical lenses) used in optical communication elements. A liquid ejecting apparatus that ejects a liquid onto the substrate or a liquid ejecting apparatus that ejects an etching solution such as an acid or an alkali to etch the substrate may be employed.

  The present invention is not limited to the above-described embodiments and modifications, and can be realized with various configurations without departing from the spirit thereof. For example, the technical features in the embodiments and the modifications corresponding to the technical features in each embodiment described in the summary section of the invention are to solve some or all of the above-described problems, or In order to achieve part or all of the effects, replacement or combination can be performed as appropriate. Further, if the technical feature is not described as essential in the present specification, it can be deleted as appropriate.

10 ... Host computer 20 ... Color inkjet printer (printer)
24 ... paper feed roller 26 ... platen plate 28 ... carriage 30 ... carriage motor 32 ... traction belt 34 ... guide rail 40 ... print head (ejection unit)
41 ... Ink cartridge 41c ... Ink cartridge 41k ... Ink cartridge 41m ... Ink cartridge 41y ... Ink cartridge 45p ... Nozzle surface 50 ... Interface 52 ... System controller 52a ... Print controller 52b ... Maintenance controller 54 ... Main scan driver 56 ... Sub scan driver Scanning drive unit 60 ... Head drive unit 62 ... Nozzle inspection drive unit 64 ... Wiper drive unit 100 ... Nozzle inspection unit 102a ... Light emitting element 102b ... Light receiving element 200 ... Ink suction part 210 ... Ink receiving container 300 ... Wiper part 312 ... Wiper blade 312e ... Tip 314 ... Wiper holder P ... Printing paper (medium)
NL ... Nozzle array MP ... Maintenance position NZ ... Nozzle

Claims (8)

A droplet discharge device for recording dots on a medium,
A discharge section for discharging droplets;
A main scanning direction recording operation for recording dots by ejecting the droplets along the main scanning direction of the medium, and the medium and the ejection unit relative to each other in the sub-scanning direction intersecting the main scanning direction. A multi-scanning operation is executed to complete the printing of dots positioned on one main scanning line along the main scanning direction by N times (N is an integer of 2 or more). A control unit that controls a printing operation for recording dots on the medium by performing pass recording, and a maintenance operation for performing maintenance on the ejection unit;
With
The controller, when performing a plurality of maintenance operations, performs at least (N-1) main scanning direction recording operations from the execution of the previous maintenance operation to the execution of the next maintenance operation. A droplet discharge apparatus that controls to execute the above. The droplet discharge device according to claim 1,
The main-scanning direction recording operation is a droplet discharge device that discharges the droplets from the discharge unit while relatively moving the discharge unit and the medium in the main scan direction. The droplet discharge device according to claim 1 or 2,
The time during which the printing operation is interrupted by one maintenance operation is limited to an allowable time or less,
Maintenance processing for which the time required for completion is equal to or greater than the allowable time is divided into a plurality of maintenance operations equal to or less than the allowable time.
A droplet discharge apparatus characterized by the above. A droplet discharge device according to any one of claims 1 to 3,
The controller is
The printing operation is controlled in _one of a first mode in which the parameter N of the multi-pass printing is N ₁ and a _second mode in which N ₂ (N ₂ is an integer larger than N ₁ ). Is possible,
In the first mode, at least (N ₁ −1) times of the main scanning direction recording operations are performed between the execution of the previous maintenance operation and the execution of the next maintenance operation. To control and
In the second mode, at least (N ₂ −1) times of the main scanning direction recording operation is executed after the previous maintenance operation is executed until the next maintenance operation is executed. A droplet discharge device characterized by controlling as described above. The droplet discharge device according to claim 4,
The first number of times and the second number of times are set to the same value.
A droplet discharge apparatus characterized by the above. It is a droplet discharge device according to any one of claims 1 to 5,
The maintenance process includes
(I) Nozzle inspection for inspecting the nozzle state of the ejection unit;
(Ii) flushing for idly ejecting droplets from the ejection unit;
(Iii) wiping for wiping off the surface of the discharge unit provided with the nozzle;
A droplet discharge device comprising at least one of the above. The droplet discharge device according to any one of claims 1 to 6,
The liquid droplet ejection apparatus, wherein the liquid droplet is an ink containing a resin. A main scanning direction recording operation for recording dots on the medium by discharging droplets from the discharge section along the main scanning direction of the medium, and the medium and the discharging section in the sub-scanning direction intersecting the main scanning direction. The main scanning direction recording operation is performed N times (N is an integer equal to or greater than 2) for recording dots positioned on one main scanning line along the main scanning direction. A droplet discharge method for performing a printing operation for recording dots on the medium and a maintenance operation for performing maintenance on the discharge unit by performing multi-pass recording completed in
When performing a plurality of maintenance operations, at least (N−1) times of main scanning direction recording operations are performed between the execution of the previous maintenance operation and the execution of the next maintenance operation. A method for ejecting liquid droplets.

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